The present disclosure relates to systems and methods that process signals over a cable transmission network.
Although Cable Television (CATV) networks originally delivered content to subscribers over large distances using an exclusively RF transmission system, modern CATV transmission systems have replaced much of the RF transmission path with a more effective optical network, creating a hybrid transmission system where cable content originates and terminates as RF signals over coaxial cables, but is converted to optical signals for transmission over the bulk of the intervening distance between the content provider and the subscriber. Specifically, CATV networks include a head end at the content provider for receiving RF signals representing many channels of content. The head end receives the respective RF content signals, multiplexes them using an RF combining network, converts the combined RF signal to an optical signal (typically by using the RF signal to modulate a laser) and outputs the optical signal to a fiber-optic network that communicates the signal to one or more nodes, each proximate a group of subscribers. The node then reverses the conversion process by de-multiplexing the received optical signal and converting it back to an RF signal so that it can be received by viewers.
Cable television (CATV) networks have continuously evolved since first being deployed as relatively simple systems that delivered video channels one-way from a content provider. Early systems included transmitters that assigned a number of CATV channels to separate frequency bands, each of approximately 6 MHz. Subsequent advancements permitted limited return communication from the subscribers back to the content provider either through a dedicated, small low-frequency signal propagated onto the coaxial network. Modern CATV networks, however, provide for not only a much greater number of channels of content, but also provide data services (such as Internet access) that require much greater bandwidth to be assigned for both forward and return paths. In the specification, the drawings, and the claims, the terms “forward path” and “downstream” may be interchangeably used to refer to a path from a head end to a node, a node to an end-user, or a head end to an end user. Conversely, the terms “return path”, “reverse path” and “upstream” may be interchangeably used to refer to a path from an end user to a node, a node to a head end, or an end user to a head end.
Simultaneous transmission of respective signals along each of a forward path and a return path requires that electronic components in the transmission network be configured to isolate the frequencies dedicated to the forward and return path, respectively. As bandwidth requirements for these paths increase over time, significant costs are incurred in upgrading components to be configured to the new splits between frequency bands devoted to the forward path and the return path. It would be desirable to reduce such costs.